1. Field of the Invention
The present invention relates to a receiver for digital voice broadcasting.
2. Description of Related Art
Recently, it has been proposed that voice broadcasting should be digitalized, that is, a voice information signal is sent as a digital voice information signal to improve the quality of voice information. In particular, digital voice broadcasting, that is, digital voice broadcasting (DAB) complying with the Eureka 147 standard has already been made to fit for practical use in European areas.
The DAB is provided with a function to allow broadcasting stations to control the gain of an audio signal line in a receiver.
This function is called DRC (dynamic range control). To implement the DRC, broadcasting stations send control data called DRC data together with the original voice data. That is, a two-byte area called F-PAD is provided at the end of frames of digital voice data, and DRC data, placed therein, is sent. For example, in the case of mode II, since a frame cycle is 24 ms, DRC data is sent every 24 ms.
The DRC data is 6 bits in size and the relationship between the DRC data and the gain of an audio signal line is as shown below.
DRC data Gain 000000:0 dB (reference gain) 000001:+0.25 dB 000010:+0.50 dB 000011:+0.75 dB . . . .rarw. Incremented every 0.25 dB step in this section 111111:+15.75 dB
Incremented every 0.25 dB step in this section 111111:+15.75 dB
That is, if "000011" is sent as DRC data from a broadcasting station, the gain of an audio signal line is increased by 0.75 dB, so that the level of an audio signal becomes 0.75 dB higher than a user-specified level.
Accordingly, a DAB receiver can, by performing DRC processing using a Digital Signal Processor (DSP), offer music broadcasts excellent in dynamics, one of audio effects. Also, even inexpensive DSPs can be expected to offer the same effect as brought about by an effector using an advanced DSP.
DRC having the above described functions and effects is effective, for example, when enjoying music in noisy environments such as inside a running car.
However, for example, in the case of a running car, DRC intended by a broadcasting station and listener-desired DRC may differ depending on running environments, such as running on a general road or autobahn, car type, and weather (fine or rainy). Also, DRC data may not be contained in a broadcast itself.
Accordingly, a DSP for DRC processing, provided in a DAB receiver, may merely make the receiver more costly and provide no significant effects.